The present invention relates generally to a growth factor precursor and its use to select production of antigen specific catalytic antibodies. Such catalytic antibodies are produced following B cell activation and proliferation induced by catalytic cleavage products of a target antigen portion of the growth factor precursor of the present invention. A particularly useful form of the growth factor precursor is as a nucleic acid vaccine. The nucleic acid vaccine of the present invention preferably further comprises a molecular adjuvant. Another aspect of the present invention comprises a growth factor precursor in multimeric form. The growth factor precursor of the present invention is useful for generating catalytic antibodies for both therapeutic, diagnostic and industrial purposes.
The rapidly increasing sophistication of recombinant DNA technology is greatly facilitating research and development in the medical and allied health fields. A particularly important area of research is the use of recombinant antigens to stimulate immune response mechanisms and outcomes. However, recombinant techniques have not been fully effective in generating all components of the humoral response. One such important yet not fully exploited component is the catalytic antibody.
Catalytic antibodies are highly substrate specific catalysts which can be used, for example, to proteolytically activate or inactivate proteins. Catalytic antibodies have great potential as therapeutic agents in human diseases such as rheumatoid arthritis, AIDS and Alzheimer""s disease amongst many others.
Antibody therapy has been used in patients. Antibodies have a half-life of about 23 days in the circulation of humans which is a clear advantage over other drugs. Catalytic antibodies, however, are considered to be even more effective. They are recycled after their antigenic encounter and are not bound to the antigen as occurs with xe2x80x9cclassicalxe2x80x9d antibodies. Catalytic antibodies should, therefore, function at a much lower dose than classical antibodies and could be used at sub-immunogenic doses. Catalytic antibodies would be particularly useful in long term therapy.
Traditionally, catalytic antibodies have been generated by immunising mice with transition state analogs. Such antibodies have been shown to catalyse several chemical reactions. However, this approach has a severe limitation in that it is difficult to predict the structure of transition state analogs which effect proteolysis of specific proteins. Immunising a mouse with a transition state analog is by definition inefficient since it selects B cells on the ability of surface immunoglobulins to bind the analogs and not on the ability of a surface immunoglobulins to catalytically cleave the analogue. This is one of the reasons why catalytic antibodies have relatively low turn-over rates and cannot compete with the naturally occurring enzyme counterparts, in the case where they exist.
Another approach has been the mutation of conventional antibodies to alter their activity to be catalytical like in nature. However, to date, such an approach has not proved successful.
As a consequence, catalytic antibodies have not previously achieved prominence as therapeutic, diagnostic or industrial tools.
There is a need, therefore, to develop a more efficacious approach to generating catalytic antibodies having desired catalytic specificity.
International Patent Application No. PCT/AU97/00194 filed on Mar. 26, 1997 and is herein incorporated by reference provided a means for selecting catalytic B cells. The method contemplated a growth factor comprising two Ig binding domains from protein L of Peptostreptococcus magnus as B cell surface molecule binding portions flanking a T cell surface molecule binding portion (designated xe2x80x9cHxe2x80x9d) from hen egg lysozyme (HEL). The specificity of the LHL growth factor for catalytic B cells was provided by an antigen masking or attached to a molecule masking one or more of the B cell surface molecule binding portions. Catalytic cleavage of the antigen exposed the B cell surface molecule binding portions to permit catalytic antibody production.
In accordance with the present invention, there is provided an improved growth factor precursor.
Throughout this specification, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.
Sequence Identity Numbers (SEQ ID NOs.) for nucleotide and amino acid sequences referred to herein are defined following the Examples.
One aspect of the present invention is directed to a growth factor precursor comprising a recombinant polypeptide chain or a molecule having modular peptide components or a synthetic equivalent thereof wherein said polypeptide chain or modular peptide molecule comprises at least one B cell surface molecule binding portion, at least one T cell surface molecule binding portion capable of providing T cell dependent help to a B cell, an antigen cleavable by a catalytic antibody and a peptide portion comprising domains from both a variable heavy chain and a variable light chain of an immunoglobulin and wherein said variable heavy chain and variable light chain domains in the growth factor precursor, associate together by intra- and/or inter-domain bonding and substantially prevent the at least one B cell surface molecule binding portion from interacting with a B cell surface molecule such that upon cleavage of said antigen by a catalytic antibody, the peptide comprising said variable heavy chain and variable light chain domain permits the at least one B cell surface molecule binding portion to interact with a B cell surface molecule.
Another aspect of the present provides a growth factor precursor comprising a recombinant polypeptide chain or a molecule having modular peptide components or a synthetic equivalent thereof wherein said polypeptide chain or modular peptide molecule comprises at least one B cell surface molecule binding portion, at least one T cell surface molecule binding portion capable of providing T cell dependent help to a B cell, an antigen cleavable by a catalytic antibody and a peptide portion comprising domains from both a variable heavy chain and a variable light chain of an immunoglobulin and wherein said variable heavy chain and variable light chain domains in the growth factor precursor associate together by intra- and/or inter-domain bonding and substantially prevent the at least one B cell surface molecule binding portion from interacting with a B cell surface molecule such that upon cleavage of said antigen by a catalytic antibody, the peptide comprising said variable heavy chain and variable light chain domain permits the at least one B cell surface molecule binding portion to interact with a B cell surface molecule wherein if said growth factor precursor comprises a single B cell surface molecule binding portion, then the growth factor precursor further comprises a multimerising inducing element.
Yet another aspect of the present invention provides a growth factor precursor comprising a recombinant polypeptide chain or a molecule having modular peptide components or a synthetic equivalent thereof wherein said polypeptide chain or modular peptide molecule comprises at least two B cell surface molecule binding portions, at least one T cell surface molecule binding portion capable of providing T cell dependent help to a B cell, an antigen cleavable by a catalytic antibody and a peptide portion comprising domains from both a variable heavy chain and a variable light chain such that in the growth factor precursor, these variable chain domains associate together by intra- and/or inter-domain bonding and, when associated together, substantially prevent at least one of the B cell surface molecule binding portions from interacting with a B cell surface molecule wherein upon cleavage of said antigen by a catalytic antibody, the at least two B cell surface molecule binding portions induce activation and proliferation of a B cell expressing said catalytic antibody.